idcode 00000000000000000000000000000000
Is this the first time you've used iMPACT? It can be confusing. Lots of things can go wrong and cause IDCODE of 0.
Does iMPACT work fine on other boards, or do you have only one board?
Which version of iMPACT are you using? I'm using 9.1.03i for Windows.
Which download cable are you using?
When you launch iMPACT, click "create a new project", then select "Configure devices using Boundary-Scan (JTAG)" and "Automatically connect to a cable and identify Boundary Scan chain", and click "Finish". It should locate your download cable, connect to the board, and then display a diagram showing the chain of JTAG devices on your board. It should also prompt you for the filenames that you want to download into your devices. If that doesn't happen, look in the text status window for suspicious messages.